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Fishes saving coral

BBC ‘Blue Planet – Deep Trouble’ team explain the environmental dangers facing the world’s shallow waters. With high demands for rare species of fish, coral reefs are in danger of being fished out and deserted.

When coral are threatened by encroaching toxic algae, they do not have the luxury of running from their enemy. That is not to say these stationary creatures are defenseless, though. Acropora coral has evolved to emit a chemical call for help, and within minutes, a goby fish will show up on the scene, ready to nibble off the algae. Researchers recently discovered this underwater partnership in the waters near Fiji. They say this symbiotic relationship is the first known example of a species chemically signaling another in order to remove a competitor species.

The fish’s response time is short because the goby fish are never far away from the coral. Nestled in the crevices of the reef, protected from predators, goby fish feast on a smörgåsbord of local fares: coral mucus, algae and zooplankton. In return, the goby is available for minor coral maintenance issues like mowing the toxic algae lawn. This task is pretty simple for the fish—one species of goby observed in this study ate the stuff and another just trimmed it off—and important for the coral.